Radio frequency (RF) wireless communications use wireless transfer of RF waves to communicate and transfer information and can be used in a wide range of applications. For example, RF wireless communications can be used to provide interactive broadband access for data and file transfer, GPS services, web surfing, video capture, streaming video, Internet commerce, Internet gaming, and electronic books. Other examples for applications of RF wireless communications include radar, RF imaging, space communications, RF targeting, RF sensor networks, RF surveillance, and various uses of wirelessly directing RF waves from one location to another. Some specific uses of RF wireless communications are static and mobile RFIDs, inventory tracking and control, and security monitoring at security checkpoints such as airports and shipping ports.
RF wireless signals can be transmitted between two communication devices or nodes through a transmission channel. The transmission channel includes the electronics and antennas of an RF transmitter at the first node. The actual transmission medium is also part of the transmission channel, including various objects which reflect or scatter the wireless RF signals. Also part of the transmission channel are the electronics and antennas of an RF receiver at the second node. Interactions, such as reflecting and scattering, with any encountered objects which are part of the transmission channel can affect the transmission of the wireless RF signal to the RF receiver and the detection of the received wireless RF signal at the RF receiver.